1. Field of the Invention
The present invention relates to an ink-jet recording head, and more particularly to an ink-jet recording head and an ink-jet recording apparatus which have a wiring pattern formed on a wiring board for supplying electric power to an actuator.
2. Description of the Related Art
As disclosed in the Japanese Patent Application Laid-open No. 2003-159795, an on-demand type ink-jet recording head of the conventional art includes a cavity unit and a piezoelectric actuator. The cavity unit is formed by laminating a plurality of plates and has a plurality of pressure chambers arranged in two rows or arrays. The piezoelectric actuator is joined to the cavity unit and has active portions (energy generating devices), each of which is associated with one of the pressure chambers. The piezoelectric actuator also has surface electrodes formed on its top surface thereof along both side edges in a longitudinal direction thereof. Each of the surface electrodes is associated with one of the active portions of the piezoelectric actuator to apply voltage to the active portions. The joining terminals (joining electrodes) on a flexible flat cable for transmitting control signals from an external source are overlapped with and are joined to the surface electrodes of the piezoelectric actuator.
The flexible flat cable extends in an extending direction of the piezoelectric actuator and has a large number of wirings connected to the two rows of joining electrodes (joining terminal portions). The wirings are formed on a narrow portion (width in a direction perpendicular to the longitudinal direction) of the flexible flat cable and are extended outwardly. Common joining electrodes are arranged at the outer ends of the wirings at the rows of joining electrodes. The wirings extending from the individual joining electrodes, each of which is connected to one of the active portions, pass between the two common joining electrodes in the width direction of the flexible flat cable. As a result, the width of the wirings including the common wiring in the flexible flat cable becomes extremely fine, and that the gaps therebetween become extremely narrow. Particularly, with the recent widespread use of color recording and high-speed recording, recording heads are formed with four to six rows of nozzles. Accordingly, in proportion to the increase in the number of nozzles and the number of joining electrodes, the distance (gap) between wirings, and the distance between the wirings and the common joining electrodes (joining terminals) are becoming narrower. This causes a problem of an increase in mutual inductance generated between adjoining wirings thereby degrading recording performance.
Therefore, as disclosed in Japanese Patent Application Laid-open No. 11-147311, it was conceived to realize a high integration of wirings by forming a flexible circuit board with a plurality of laminated substrate layers having wirings on one side, forming an opening in at least one of the substrate layers, exposing the wirings on the substrate layers that are formed on the backside via the opening to form joining electrodes, and joining these joining electrodes to surface electrodes for individual electrodes.
The inventor of the present invention disclosed an ink-jet recording head having a plurality of nozzle rows in U.S. Pat. No. 6,715,862 and U.S. publication No. 2004-0125177A1, which disclose extending a wiring board which supplies electricity to discharging energy generating means, each of which is associated with a nozzle, in a direction perpendicular to the nozzle rows, and extending wiring from individual joining electrodes, each of which is connected to one of the energy generating means, in a direction perpendicular to the nozzle rows. This results in the common joining electrodes extending along the side edges of the wiring board to mutually connect the ends of the plurality of rows of energy generating means. The wirings that extend from the individual joining electrodes in one row are bent to pass between the individual joining electrodes in another row.
The inventor discovered that in such wirings extending from a part of the individual joining electrodes need to pass between the individual joining electrodes in another row and the common joining electrodes, so that the space between the wirings and the common joining electrodes is extremely narrow, resulting in increased mutual inductance as stated above.